During the past 10 to 15 years, contact lenses have tended to replace glasses for correcting vision problems. These days, an entire industry exists for contact lens manufacturing and retailing.
One of the problems associated with contact lenses is marking the lens in order to allow the users to wear them properly, in the right position. Some lenses have to be worn in an "upright" orientation while soft lenses must be worn without inverting them, i.e. wearing them inside-out. Generally, identification and orientation marks applies to all kinds of contact lenses.
Various methods of contact lens identification are known in the prior art. One method is printing a visible mark on the periphery of the lens. However, this method is not suited for wet molded soft lenses since the printing must be performed on a dry surface and the lenses are never in a dry state. Furthermore, the dark mark printed on lenses may be too visible, so observers may even see the mark when the lens is worn by a person.
Another method is to engrave or impart a mark on a lens producing an opaque surface. However, this surface is necessarily rough and may be felt by the wearer, thus producing discomfort. The engraved mark may also attract and retain proteinaceous and other types of deposits creating propitious conditions for an infection.
Another method of marking contact lenses is to mark them using a laser. However, this method cannot be employed for wet molded soft contact lenses. It is also time-consuming and expensive.